The present invention broadly relates to a method of continuously winding a yarn or the like on bobbins and automatically exchanging a full bobbin with an empty bobbin and pertains, more specifically, to a new and improved method of continuously winding at least one filament or thread and automatically changing bobbins in an automatic winder or winding machine having at least two bobbin mandrels, each provided with a self-contained drive, and a contact or friction drive roller which is in contact with a package being formed on one of the at least two bobbin mandrels during the normal winding operation. The contact or friction drive roller is also provided with a self-contained drive. The present invention also relates to a new and improved apparatus for performing the inventive method of continuously winding at least one filament or thread and automatically changing bobbins in an automatic winder or winding machine.
An automatic winder of this type for continuous loss-free or wasteless winding of monofilaments or multifilaments, particularly, but not exclusively, synthetic or man-made filaments, comprises at least two bobbin mandrels, one of which is used for winding the filament, while the other bobbin mandrel is held in a stand-by position so that the filament, subsequent to completing the package being wound on the first bobbin mandrel, can be transferred to the second bobbin mandrel to continue the filament winding operation, thus accomplishing the exchange of bobbins. In the case of high filament delivery speeds, for example, speeds above 4000 m/min., it can be advantageous to provide each bobbin mandrel with self-contained drive means, such drive means being a spindle drive or direct drive, i.e. surface drive of the package itself. Nevertheless, during the normal winding process, the filament travels around a so-called contact roller or friction drive roll and then onto the package of the bobbin mandrel in the operating or working position. This contact roller exercises a predetermined surface or contact pressure on the package being formed and possibly also serves as a guide for the filament or thread between a traverser or traverse device and the package, and/or supplies a signal representing the circumferential speed of the package to a control unit for the bobbin-mandrel drive.
During the normal winding process, i.e. the so-called winding travel, the contact or friction drive roller maintaining contact with the package being formed and the rotational speed of the contact or friction drive roller is controlled such that the circumferential speed of the contact or friction drive roller is maintained substantially equal to the linear delivery speed of the filament or thread. This contact between the contact or friction drive roller and the package is interrupted during the change of bobbins and must be restored subsequent to the bobbin change operation. A method pertinent thereto is described, for example, in U.S. Pat. No. 4,548,366, granted Oct. 22, 1985 of the assignee Rieter Machine Works Ltd., located in Winterthur, Switzerland, and in the cognate European Patent Application No. 0,182,389, published May 28, 1986 and in the further cognate European Patent Application No. 0,200,234, published Dec. 10, 1986.
The bobbin changing process is a delicate or critical operation which is particularly afflicted with the risk of a breakdown of the filament or thread tension. In order to reduce this risk, the circumferential speed of the full package during the change of bobbins in an automatic winder with spindle drive or direct drive can be readily maintained substantially constant subsequent to the interruption of contact between the contact or friction drive roller and this full package and until the filament or thread is transferred to the other bobbin mandrel. In this connection, reference is made, for example, to U.S Pat. No. 4,487,374, published Dec. 11, 1984 and the cognate European Patent No. 0,080,076, published June 1, 1983. However, in order to carry out the change of bobbins, it is necessary to interrupt the traverse motion of the filament or thread. This represents a reduction of the effective "receiving or take-up speed" for the filament or thread, this causing a corresponding reduction of the filament or thread tension. This effect or result has not been taken into account in the state-of-the-art.